Actually I posted this a long time back and got many of the same answers.My car feels better,or it runs funny on regular.Well since I broke my motor down I checkd out the pistons.Stock ls 9:1 compression running on 87 and most time 93.Well the motor was about 8years old.But the pistons were still all carbed up,But my friend has ctrs and he runs premium all the time.He took his motor apart and the pistons were spotless.Also even with premium his spark plugs still detonated,so I guess premium really doesnt help that much.My new setup comp. around 11 so I will be running on midgrade or premium.I cant tell the difference between when I pump premium and regular.But if Honda said do it I'd rather be safe then sorry.